1. Field of the Invention
The present invention relates to a control system for a boat having plural propulsion units provided side by side, which synchronizes engine speeds of the respective propulsion units with each other.
2. Description of the Related Art
One conventional boat has three propulsion units, such as outboard motors, stern drives or inboard-outdrive arrangements, provided side by side at its stern. In this type of boat, there typically are provided three shift/throttle lever pairs associated with corresponding ones of the individual propulsion units. Operating the six levers in addition to a steering wheel is cumbersome and can be troublesome to the operator.
To address this issue, one recently proposed control system uses two adjacent left and right operation levers to control shift and throttle operations of all of the plural propulsion units. With the operation levers tilted at equal angles, if the engines of the left and right propulsion units rotate at different speeds, a motor of a throttle actuating unit is actuated so as to equalize the engine speeds of the left and right propulsion units with respect to the engine speed of the right propulsion unit. As such, the engine speeds of the left and right propulsion units are synchronized with each other automatically (See Japanese Publication No. JP-A-2000-313398).
As described above, with the left and right operation levers tilted at equal angles, the control system synchronizes the engine speeds of the respective propulsion units with each other. However, there are circumstances in which the left and right operation levers are operated differently and are tilted at different angles. For example, when the boat turns left or right, the left and right operation levers are operated in opposed directions, and the operation levers thus are not tilted at equal angles. No control systems have been contemplated that synchronize the engine speeds of the respective propulsion units with each other in consideration of such an operating environment and operation conditions.